This TSB article is being republished in its entirety to add 1998-99 model year vehicles.

ISSUE:

An underhood “buzzing” noise may be heard during air suspension operation. This may be caused by:

the air pump lines being routed too close to the front end sheet metal

the wheelhouse inner may be sensitive to vibration input of air suspension compressor

ACTION:

Wrap the air lines with foam tape and place mastic applique on sheet metal under air suspension compressor. Refer to the following Service Procedure for details.

SERVICE PROCEDURE

NOTE:

FOAM TAPE MUST BE PLACED ON THE AIR LINES IN A LOCATION THAT WILL PREVENT THE AIR LINES FROM CONTACTING ANY SHEET METAL.

Wrap the air lines with 12.7×101.6mm (1/2×4″) Foam Tape (Rotunda Squeak and Rattle Repair Kit PVC Foam Tape 164-R4901, or obtained locally) at the locations shown in Figure 1. Expedition/Navigator 4X2 and F-250 will need to be wrapped at A and B in Figure 1. Expedition/Navigator 4X4 will require tape at A, B, C, and D in Figure 1.

If no groundouts are found, remove air compressor and place Mastic Appliques (XL1Z-3C244-AA and XL1Z-3C245-AA) on sheet metal under air suspension compressor at A and B in Figure 2. Place appliques as follows:

Accurately place mastic onto sheet metal in a location that will not allow the cutouts for the mounting bolt to interfere with the mounting bracket. The air suspension compressor mounting bracket and the washer bottle reservoir should have complete contact with the sheet metal, and not the mastic, at the body mounting points.

CAUTION:

BE SURE TO WEAR PROTECTIVE GLOVES WHEN CONFORMING THE MASTIC TO PREVENT FINGER BURNS.

Using a heat gun, uniformly heat the mastic and apply pressure to form the mastic to the sheet metal surface.